Sensorless speed estimation of a PMSM using higher-order sliding mode observer

A sensorless speed-estimation method for the permanent magnet synchronous motor (PMSM) based on higher-order sliding mode (HSM) observer is developed in this paper. The back EMFs in the PMSM current dynamics are treated as unknown quantities and are estimated with the HSM observer. The proposed method does not require the low-pass filter. A finite-time smooth estimation is obtained and chattering phenomenon is avoided. With the direct estimation of back EMFs, an accurate estimate of speed can be obtained. Simulation results show the effectiveness of the proposed method compared to conventional method.